This invention relates to an induction system for an internal combustion engine and more particularly to an improved throttle valve for an internal combustion engine.
In many internal combustion engine induction systems it is desireable to provide a throttle valve for controlling flow through an induction passage which will insure complete closure during a certain phase of the operation. Although such a result can be obtained by maintaining extremely close tolerances, such a solution presents substantial cost penalties and in some instances excessive machining operations.
It is, therefore, a principal object of this invention to provide an improved throttle valve construction for an internal combustion engine induction system that will insure complete sealing under certain conditions.
It is another object of the invention to provide a throttle valve construction for an internal combustion engine which is effective in operation and yet low in manufacturing costs.
Recently it has been discovered that engine operation (both emission of unwanted exhaust gas constituents and fuel economy) can be improved, particularly at idle and low load operation by providing a sub-intake system through which a substantial portion of the induction charge flows to the combustion chambers under these operating conditions. By using a relatively small cross-sectional area induction system turbulence and, if desired, swirl may be generated in the combustion chamber at the time of ignition. As such, smoother and more efficient combustion results under these load conditions.
It has been proposed to control the flow through the sub-intake system by means of a main throttle valve and an auxiliary or sub-throttle valve which operate in sequence so as to cause substantially all of the idle and low load charge requirements to enter the combustion chambers through the sub-intake passage and to provide an increased flow through the main induction passage as the engine load increases. In connection with the adaptation of this concept to multiple chamber engines having multiple carburetor barrels, it has been proposed to provide only one of the carburetor barrels with a system for accommodating certain engine operating conditions. This one carburetor barrel can serve a plurality of chambers through the combined sub-intake passages, all of which are fed from this one carburetor barrel. An example of an application of this principal to a multiple cylinder engine may be found in the copending application of Hiromitsu Matsumoto, Ser. No. 838,353, entitled Control of Carburetor Supplied Induction System, filed Sept. 30, 1977 and assigned to the assignee of this application, such an arrangement being shown specifically in the embodiment of FIGS. 6-10 of that application.
With an arrangement as disclosed in that application, it is important that the throttle valves of the induction systems associated with the carburetors that serve other than the specific condition are accurately closed and do not permit any leakage during operation under the one specific condition. If these throttle valves were not fully closed, leakage might occur which would dilute the mixture strength entering the other cylinders and result in uneven running and poor overall performance.
It is, therefore, another object of this invention to provide an improved throttle construction for a multiple cylinder multiple carburetor barrel engine induction system.